bugs with elytra and fireworks through the nether portal

While playing on a superflat world on creative, when flying through the nether portal with elytra on and using fireworks to boost speed, the nether portals kept spawning weirdly and teleporting me twice, teleporting onto big distances, nether portals not spawning in inside of the nether, and nocliping through blocks, also fireworks kept getting stuck in the portals. [tried recreating this, but failed, still have the original world file]  only problem with attaching a file is that it's an almost 600MB video, I'll be glad to send it in some sort of a possible way